Giant SL1 Aero Road Wheelsystem £249.99 (front), £349.99 (rear)

For reduced drag matched with more immediate flex-free power transfer, a set of system-built aero wheels is probably the most profound road bike upgrade you can treat yourself to. The Giant SL1 wheel features a wind-slicing 55mm-deep carbon rim with alloy braking surface, and a typically Giant engineered-in upgrade called DBL – Dynamic Balanced Lacing (below).